Conventionally, a solid oxide fuel cell (hereinafter, also referred to as SOFC) using a solid electrolyte (solid oxide) is known as a fuel cell.
In the SOFC, a fuel battery cell (power generation cell) is used as a power generation unit. In the fuel battery cell, for example, an anode in contact with fuel gas is provided on one side of a solid electrolyte layer, and an oxidant electrode (cathode) in contact with oxidant gas (air) is provided on the other side of the solid electrolyte layer. Further, in order to obtain a desired voltage, a stack (fuel cell stack) has been developed which includes a plurality of power generation cells that are stacked via inter-connectors.
Usually, in the fuel cell stack of this type, power generation cells close to the middle section of the fuel cell stack have a higher temperature than power generation cells at end sections of the fuel cell stack in a direction in which the power generation cells are stacked (stacking direction). There is a problem in that temperature distribution in the stacking direction of the fuel cell stack is not uniform.
Therefore, in recent years, as described in Patent Document 1, in order to equalize temperature distribution in the stacking direction of the fuel cell stack and to increase power generation efficiency, a technique has been proposed in which cool air is supplied to one side of a center portion of the fuel cell stack (one side of a direction orthogonal to the stacking direction), and heat exchanged hot gas is supplied to end portions in the stacking direction of the fuel cell stack.